A prior-art vehicle door lock device is disclosed in Patent Document 1. The vehicle door lock device includes amounting member, a fork, a pawl, and a switching mechanism.
The mounting member is provided on a door that opens and closes an opening of a vehicle body. A striker is fixed to the vehicle body, and an entry opening that the striker enters is formed in the mounting member. The fork is pivotably provided on the mounting member. The fork is switched between a latched state, in which the striker is locked in the entry opening, and an unlatched state, in which the locking of the striker in the entry opening is released. The pawl is pivotably provided on the mounting member. The pawl is capable of fixing or allowing pivotal movement of the fork.
The switching mechanism acts on the pawl to switch the fork from the latched state to the unlatched state. More specifically, the switching mechanism includes an outside lever, which is pivotably supported by the mounting member, and an intermediate lever, which is pivotably supported at one end of the outside lever. The other end of the outside lever is coupled to an outside handle for a door-opening operation via a cable. When the other end of the outside lever is pulled upward by the door-opening operation, the one end of the outside lever and the intermediate lever are moved downward.
An engaging projection that projects downward and an engaging hole, which surrounds the engaging projection from below in a U-shape, are formed at a center of the intermediate lever. Two coil springs that face each other are provided between the intermediate lever and the mounting member. The intermediate lever is held at an initial position by the respective coil springs, and assumes a substantially vertically upright posture.
The pawl includes a ratchet abutting the fork, a rotation shaft having one of its ends integrally coupled to the ratchet, and an opening lever formed with an engaging claw portion that is integrally coupled to the other end of the rotation shaft. The engaging claw portion of the open lever is inserted into the engaging hole of the intermediate lever, and is positioned below the engaging projection.
In the prior-art vehicle door lock device having the above-described structure, when the intermediate lever is moved downward by the door-opening operation in a normal state, the engaging projection of the intermediate lever at the initial position presses the engaging claw portion of the opening lever. Therefore, the pawl pivots about the rotating shaft, the ratchet moves away from the fork, and the fork is switched from the latched state to the unlatched state.
Furthermore, in this vehicle door lock device, if the door or the vehicle body experiences an impact from the outside of the vehicle due to a collision or the like towards the vehicle, an inertia force will act on the intermediate lever in the direction of impact. Therefore, because the intermediate lever pivots from the initial position in the direction opposite to the direction of impact, the engaging projection is not positioned above the engaging claw portion. In addition, in this state, an opening operation of the door occurs due to the impact, and what results is a “swing-and-miss state”, in which even if the intermediate lever moves downward, the engaging claw portion is not pressed by the engaging projection, i.e. the fork is not switched from the latched state to the unlatched state. In this manner, the prior-art vehicle door lock device prevents an unintended opening of the door at the time of impact, to ensure the safety of the passenger(s).